Lymphocytes are characterized by membrane markers which, in part, reflect biological and functional activity. This is particularly true for T lymphocyte subsets identified by monoclonal antibodies. The B lymphocytes can be identified but in a more general manner. It has been proposed that the use of these markers will aid in the differential diagnosis of a variety of lymphomas. The objective of this work was to evaluate the use of monoclonal antibodies (MAb-s) and surface immunoglobulin (sIg) analysis in a cell flow cytometer (CFC) as methods to identify and classify lymphomas. The cell flow cytometric findings were then evaluated in light of the histopathologic diagnosis (HPD). Fifty-eight (58) patients with a variety of lymphomas and benign lymph node disorders were studied. Lymph node tissue samples were obtained after surgical removal and appropriately prepared for evaluation in a CFC. Results showed that the variety of hyperplasias and reactive follicular lymphadenopathies could not be characterized by the technique or application of CFC alone. Both B cell and T cell lymphomas could be recognized and differentiated by MAb-s and/or light chain monotypism using sIg's in a CFC, but morphologic and clinical information were required for diagnostic confirmation. Hodgkin's disease could not be identified by CFC because of the lack of a specific identifiable marker. Cell flow cytometry provides an easy and rapid adjunct to the diagnosis of a variety of lymphomas. At the present time, membrane markers in cell suspensions from tissues (lymph nodes) identified by MAb-s and sIg's in a CFC cannot be used to provide definitive diagnoses for reactive lymphadenopathies, Hodgkin's disease or some classes of lymphomas.